Delay indicating apparatus



June 26, 19.51 l A MEACHAM 2,558,189

DELAY INDICATI-.NG APPARATUS /Nl/ENTOR L A. ME A CHA/M' A TTORNEV June26, 1951v A, MEACHAM 2,558,189

DELAY INDICATING APPARATUS Original Filed June 22, 1943 4 Sheets-Sheet 2,4a A IIVI/ENTOAJ LA MEAC/'IAM ATTORNEY June 26, 1951 L A, MEACHAM'2,558,189

DELAY INDICATING APPARATUS original Filed June 22,'*1943 4 sheets-sheet5 H631 .A l VV /2223\| 96 48 55 A TTO/QNEY 4 Sheets- Sheet 4 IIIII L\\\QUIESCENT PER/OD l.. A. MEAcHAM DELAY INDICATING APPARATUS /I I l l IIIIIIIILIIIII ACT/VE PER/0D nlllllllll June 26, 1951 Original Filed June22, 1943 Mal /A/vE/vron L. A MEA CHT/4M @y Arron/ffy GND.

Patented .une 26, 1951 DELAY INDI'CATIN G APPARATUS Larned A. Meacham,Summit, N. J., assigner to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New York Original application June.22, 1943, Serial No.

491,791. Divided and this application Decemher 14, 1946, Serial N0.716,295

This invention relates to pulse delay indicating apparatus andparticularly to such apparatus for producing an indication of the delayinterval separating a certain pulse of a series of pulses which areradiated, towards a distant object and a received echo pulse which `isreiiected from the distant object.

In accordance with an embodiment of the invention herein shown anddescribed for the purpose of illustration, there are provided means forgenerating, during aninterval which occurs between the time of radiationof an impulse of a series of impulses fromy a transmitter and the 4Claims. (Cl. 175-381) time of reception by a receiving apparatus of anecho of the radiated impulse from a distant object,'a series ofalternate. positive and negative impulses of brief duration recurring atpredetermined equal intervals and means for causing the selection of oneof the series of impulses by superposing it upon a pedestal impulsewhich is started under control of, and coincidentally with, the impulseimmediately preceding the selected impulse. Means are provided forvarying and measuring the delay interval 4between the time of radiationof an impulse and the time of occurrence of the selected one of theseries of impulses, the indicating means being preferably calibrated inunits of distance so that, when the selected impulse is delayed bytherequired amount to bring it into coincidence with the received echo ofthe ,radiated impulse, there is produced an indication of the distancefrom the impulse radiator and receiver to the object from which the echois received. Y

To facilitate the manual adjustment of the apparatus for bringing theselected impulse into coincidence with a received echo, a visualindieating device such as a cathode ray tube is preierably provided. Theecho impulse, together with the selected impulse or a range impulsecontrolled by the selected impulse, are impressed upon the verticaldeflecting plates, for example, of the cathode ray tube. The horizontaldeflection of the cathode ray beam produced in the cathode ray tube iscontrolled byla deecting wave or precision sweep" which is initiatedsimultaneously with the starting of the pedestal under controlrof theimpulse which initiates the pedestal. The position of the range pulse isxed near the center of the screen of the cathode ray tube; and theposition of the echo pulse, when the object is stationary and the delayadjustment remains unchanged is also accurately xed so that jittering orto andfro .movement of the ceived in rapid succession.

2 Y visual indication is avoidedV when, as is the practice, impulses areradiated and echoes are re- When the object moves, or the delayadjustment is changed, the echo appears to progress smoothly across thescreen.

The brief pulses of a' high frequency radio wave which are radiatedtoward an object are produced at intervals under control of startingpulses which may be generated under control of an alternatingelectromotive force of relatively low' frequency, say 400 cycles persecond, one starting pulse being produced at about the same point ineach cycle of the 400-cyc1e'wave.' These starting pulses are also usedforcontrolling the so-called range unit Yconstructed in accordance withthe present invention. The starting pulses are impressed upon a circuit,called a start-stop circuit herein,` which generates a square toppedvoltage Wave having a negativer portion the'duration of which is equalto or preferably greater than the maximum delay 'occurring between thetime of production of a starting impulse and the reception of an echo ofthe radiated pulse from an object the distance of which is to bemeasured. During the interval that the square topped impulse produced bythe start-stop circuit is positive the start-stop circuit is returned toits stable waiting condition ready to be started again by a succeedingstart impulse. This interval is preferably short with respect to thelength of the negative portion of the square topped wave so that rangeimpulses may loe-transmitted in rapid succession. The start-stop circuitemploys two electric discharge devices (the electrodes of which may bewithin a single envelope), the anode of one `device being connectedthrough a condenser to the control grid of the second device as in amultivibrator circuit. It has been found that by'connecting the anode ofthe second device to the control grid of the first device directly by aconductive connection instead of connecting the anode to the gridthrough a condenser as in the usual multivibrator circuit, the recoverytime of the circuit is considerablylshortened.

A timing Wave generator is started due to the abrupt decrease inpotential at the start of the negative portion of the square topped wavefrom the start-stop circuit. The generator frequency is accuratelymaintained at a constant value so that the period of one cycle will beequal at all times to the predetermined interval required vfor a rangeimpulse to travel from a radiator to an object a definite distance awayand for its echo 3 to return. Quenching of the oscillatory Wave producedby the generator is started due to the abrupt rise in potentialoccurring at the beginning of the positive portion of the square toppedwave produced by the start-stop circuit and the generator is designedAso that the quenching is completed "Within the relatively short periodof the positive portion of the square topped wave. The timing wavegenerator is coupled to a phase shifter by means of a phase invertercircuit which provides an accurately balanced W impedance input to thephase shifter and is designed' to present an extremely high impedance tothe antiresonant circuit of the timing wave generator to which it iscoupled. In order to minimize the time requirement for the phaseA`shifter to reach steady state response to each group of timingoscillations, the phase shifting circuit is designed so that it presentsa substantially pure resistance load to the output Aof thevphaseinverter circuit to which'it 'is c'olpled. The phase shiftingcn'dei'ifse 'of the phase shifter Vis an improve; ment over thecondenser disclosed in my United States Patent No. 2,004,613, grantedJune 41'1, 1'935. It is designed to simplify its manufacture, to providecomplete shielding, to avoid use of moving 'contacts and to obtainsatisfactory "capacitive balances through inherent mechanical symmetry.

The timing wave is 'supplied from the 'output of the phase shifter to anamplifier the Output of which is connected to 'a pulse generator whichp'rduces a series of alternate positive and nega'- tive sharp pulses,these pulses being accurately spaced by the predetermined 'intervalmentioned. The amplifier is a'high gain linear amplifier with negativefeedback to present an extremely high impedance 'the phase shifter andto avoid drawing an appreciable resistive` component of current throughthe small capacity of the phase shift-condenser which would causedistortion of the timing Wave. 'The Aamplified timing tva-Ve :isimpressed upon 'an electric discharge device circuitl which functionsasacathode follower VAduri-ng positive half cycles of the amplified timingwave, and which 'device is cut off during the negative half cycles toeffectively Yclip the timing V'Wave along 'its center line, the negat'vehalf of the timing Wave impressed upon the input circuit of this centerclipper ,"beig discarded. The clipped timing wave :appears with reversedpolarity in the plate circuit of this device. An electricdischargevdevice'coupled to thecenter clipper circuit is alternately cutoff Aand turned on again by the square topped portion 'of theinvertedcente'rclipped wave to producea series-of alternateipositive andnegative timing impulses. The sharp'- ness of response of the timing'pulse generator-is improved vby providing a 4'delay 'in the Vnegati-'vefeedback of the center clipper to momentarily impart high gain to thecenter clipper tubefat the beginning of each 'positive `half cycle -ofthe timing wave.

'I'he square tpped wave from fthe kstart-"stop circuit is also appliedrlt'oan RC delay `circuit to cause discharge of a capacitance Ythrough a'resistance which may"bx'a'va'ried to change the time constant of thedischarge'circu'it, 'thereby causing an exponentially rising potentialto beapplied to the ycontrol grid of van Velectric discharge device. Thefpotential difference to which the capacitance is char'gediisproportional to the'resistance of the variable resistor. The series'ofalternate'positive and negative timingimpulses are-impressed'fu'ponthe'cathode of the'velectric dischargedvice which is maintained, duringthe intervals between imi pulses, at a potential which is directlyproportional to the initial potential difference to which thecapacitance is charged. When the control grid potential of the dischargedevice has thus been increased sumcientl'y with respect to the cathodepotential, a negative pulse from the timing pulse generator willdecrease the cathode potential sufficiently to cause the dischargedevice to pass space current. A rapid decrease in potential at the anodeof the device thus takes place. The time 'of production of this negativestep or impulse is determined by the setting of the vari- "able resistor'Which controls the time constant of the condenser discharge circuit andalso by the phase shift of the series of impulses produced by`shiftin'gthe .phase of the wave from the timing wave generator.

Thenegative impulse produced at the output of the RC delay circuitcontrols a circuit for generating a 'square' topped impulse or pedestaland a sweep wave forl controlling the horizontal de iiection of acathode ray beam. The-.pedestal which is initiated vesiinzzid'eritall'yVwith a negative pulse from the 'timing 'pulse generator is added to' thetiming Vpulse with the result that the positive pulse which immediatelyfollows that 'negative pulse is sup'erposed upon 'the pedestal. Thesuperposed impulse may' therefore Abe -selected and used to perform adesired function. When a cathode ray indicator is used, the vselected`timing pulse maybe impressed 'on' 'the vertical deiiecting. means toproduce an indication o'f the range of an object from which an -echo.pulse is received, the lecho pulse also being impressed u'pon the ver'-tical deflecting means. Instead of applying the selected timing .pulse1directly to the rcathode ray tube for indicating the range, the timingpulse may be used to generate a step or notch pulse with which the echopulse may be aligned on the cathode ray tube screen Afor producing arange indication.

The shaft of the phaseshifter condenser which causes the phase of thetiming wave to be varied is geared to the shaft (jf the variableresistor of the RC delay circuit Athrough a step-down gear ratio suchthat the interval between a starting pulse and 'the following selectedtiming pulse may be varied continuously over a range starting 'from avalue near 'Zero'to a value corresponding tothe maximum range. e y Avrevolution counter associated with the shaft ofthe phase shiftingcondenser is calibratedfto indicate lthe distance to the object fromwhich an echo is received when lthe selected timing pulse is delayed bysuch an amount that it gccurs simultaneously with the received echo.

If desired, apparatus may be 4employed .for automatically varying thecapacity of the condenser of the phase shifter yand the variableresistor of the -delay circuit when the received echo falls out of-synchronism with `the selected timing pulse to maintain ythe echoandthe selected timing lpulse in 'synchronism Suchfan'apparatus isdisclosed in an application of B. M. Oliver Serial No. 191;829, AfiledvJune l22, y1943.

The invention `will nowbe 'described with reference tothe accompanyingdrawing in which:

"Fig, 1 isa block diagram of a ranging system .in accordance with" the'present invention Fig. TlA consists o'f curves to which reference wil-116e-made 1in describing the invention;

Figs. v'2-a1'1d3, WThenlFig.' 23 'is lplaced below Fig. i2, are la fschematic Vview -`o`f -a ran'ge vindicator in Ia'c cord'ance r`with theinventin; f

'.Fig. 4 is a schematic view oa modification 'of a portion of theapparatus shown in Fig. 3;

Fig. 5 is a view in elevation of a phase shifting condenser which isused in the range indicator of Figs. 1, 2 and 3;

Fig. 6 is a sectional View taken along the line 6-6 of Fig. 5; and

Fig. 7 is a diagram to which reference will be made in explaining theoperation of the invention.

Referring now particularly to Figs. 1 and 1A, there is disclosed a rangeindicating system in which recurring brief pulses of electromagneticwave energy produced by a radio transmitter I andradiated froman antennaare directed toward an object the distance of which is to bev determinedand in which the reflected wave impulses or echoes are received by anantenna I2 and detected by a radio receiver I3. An oscillator I 4produces a sinusoidal Wave having a period somewhat longer than the timerequired for a radio wave to travel twice the maximum distance tov bemeasured. Starting pulse generator I produces sharp impulses asindicated at a in Fig. 1A at regular intervals, one for each cycle ofthe sine wave from oscillator I4. It is not essential to the operationof the system, however, that these impulses be produced at regularintervals. The starting impulses which are preferably of very briefduration, say 71A; microsecond, key the radio transmitter I to causecorresponding pulses of high frequency radio wave-energy to be radiatedfrom the antenna II. y

The starting pulses a are impressed upon the start-stop circuit I6 of arange unit (which comprises apparatus within the area defined by thedash-dot line IS) for generating a square topped voltage wave b. Theinitial negative portion I1 of wave b is started at the time of a startimpulse a, that is at time to, and has a duration slightly longer thanthe time required for a radiated wave pulse to travel twice the maximumdistance to be measured. The start-stop circuit then recovers its stablewaiting condition during a' period which is short with respect to itsactive period during which the negative impulse Il is produced. Thepositive portion I8 of the wave b is produced during this recoveryperiod.

l If the frequency of oscillator I4 is varied below a certain maximumvalue, the duration of the negative portion I'I remains fixed, whilethat of the positive portion I8 varies, above a certain minimum durationfor recovery.

The voltage wave b produced by the start-stop circuit i3 is impressedupon a timing wave generator 2U which generates a constant frequencyoscillatory wave c the phase of which may be shifted by a phase shifter2| continuously through a plurality of cycles by turning the handle |26.The phase shifted wave is indicated at d. The period of this oscillatorywave or a phase shift of the wave through a single cycle corresponds tothe time interval required for a radiated wave to travel through acertain distance and for its echo to return through that distance. Thedistance represented by the period of a single cycle of the oscillatorywave is the velocity from the phase shifter is impressed upon a pulsegenerator 22 which produces alternate positive,

and negative timing pulses as indicated at e of Fig. 1A, a pulse beingproduced at the beginning of each half cycle of the timing wave.

It' is desired to produce a pedestal impulse upon which a certain one ofthe timing impulses may be 'superposed so that that timing impulse maybe'selected and used. Means are required for shifting the pedestal withrespect to time in synchronism with the shifting of the timing impulsesso that one impulse of each series of impulses may be superposed uponthe pedestal. There is provided an RC delay circuit 23 having acondenser which is discharged, at a rate-determined by the' setting of avariable resistor, during the period defined by the portion |I of thewave b from the start-stop circuit IS. The shaft 34 of the variableresistor of the RC delay circuit is connected through gears 24 to thecondenser shaft 29 of the phase shifter 2| so that the change in timeconstant of the condenser disl charge circuit is proportional to thephase shift ofthe timing wave d and of the timing impulses e. The timingimpulses e are also impressed upon the RC delay circuit for accuratelyfixing the time of generation of the pedestal impulse and the sweepwave.

A voltage impulse produced at the output of the RC delay circuit asindicated by the curve |34 of Fig. 7, is impressed upon the `pedestaland sweep wave generator 25. There is produced by this circuit apedestal pulse g and a sweep wave h each of which accordingly is startedat the time of the negative pulse which immediately precedes thepositive pulse which is to be selected for use in producing a rangeindication.- The pedestal pulse g and the pulses e from the pulseVgenerator 22 are combined to cause a certain positive pulse 26 of thetiming pulses e to be superposed upon the pedestal 21 as shown at z' so4that the pulse 2B may be used to produce a range indication. Theselected timing pulse 28 may be used directly for range indication or,as shown in Figs. 1 and 1A a step impulse y may be produced undercontrol of the selected pulse 26 by the step generator 28. The sweepwave is amplied by an amplifier 35.

The step 7' and the echo impulse from the radio receiver I3 areimpressed upon the vertical deflecting plates 3| of a cathode ray tube30. The sweep wave h is impressed upon the horizontal deecting plates 32of the cathode ray tube. By manually rotating the shaft 29 of the phaseshifter condenser to which the shaft 34 of the variable resistor of theRC delay circuit is geared, an echo pulse may be caused to travel alongthe luminescent screen of the cathode ray tube until it is brought intoalignment with the step 'JZ The distance to the object from which theecho is received may then be read from a revolution counter or rangeindicator |50 attached to the shaft 29, each revolution of the shaftproducing an indication equal to a certain fixed distance. As pointedout above, the received echo and the selected timing pulse may also beused, if desired, to control automatic apparatus which causes the shaft29 to rotate when the distance to an object from which the echo is beingreceived changes so that the changing range of the object can be readfrom the Vindicator |53 without requiring manual adjustment of theapparatus.

Y The range indicating apparatus is shown in greater detail in Figs. 2and 3 when Fig. 3 is asset-ies placed @below Fig. i12. f Currentffromf aAcycie sou-ree CI lI *isf-supplied f-to the primary 'windings offtransformersfleandi I `of Hthestarting -lpulse g-enenatorv- |55nemployinga .gaseousfiiischarge device 62 havingancano'de,iaccathode,and ancontrol 1 grid. lVoltage @from the; secondary .'ywlinding of--transformer-i6 I-is supplied tofthe :control electrede-cathode circuitottube -`i2-through` asuitable-phase shifting circuit comprising v:aishunt condenser 63, `internal f-impedances of transformerf6 I ,aand a1protective"rresistorfu 64 suchz-th'at the fcritical'fgridvoltagelfrequired to .cause scurrentf-conduction through v.the discharge`Vtube eis reached Wheni'the anode isiat or Ynearthe positive peak-vof@the f voltage lwave applied to lthe f anode circuitf'from i thesecondary `'winding f of Altransformer 6I). "Af500i1microm-icrofarad fcondenser' ismcb'arged through -aseriescircuit connecte'ditothe-secondary Winding of V'transformer#'60 Vwhich comprises-` 12000l'ohm -fresistorl land l'1.800 'ohm resistor `61. Whenthe criticalz:grid @voltage of theftubeZ is v reached, Jcondenser-iw dischargesthrough I-a circuit llcomprising inductance .element `68 lof 50vmicrohenries,'1anode-cathcdef--path of-thetube 62 a 1324A-microfaradfcondenser t9 having '30,000 vohm resistor ffm-:connected einparallel therewith and thence through lSOOphmri'es'istor 6l. Thecondenser 65 is thusfquickly-discharged (in about 1A; vmicrosecond)su-iiiciently to cause thefvoltage at the-anode of tube-e2 to be reducedand.' the vdischarge currentlthroughthe `tubez-tc be interrupted.The-radio transmitter. I comprises atniulticavity magnetron WhichfmayfbeIoi the type disclosed --in'lPatent 2,063g342-'t0 Samuel/December '-8,y11936, 'or example. The lmagnetron comprises van anode 'I I whichfforms1an external sheathor enclosure, `a cathode "I2, a loop '5i-3 and -amagnet 'I-4. `The1=anode`1l and. one fend o'f `the-1091313 are=grounded,the-other end off-the loop being lconnected through a coaxial conductorcable'l -to antenna I I. Duri-ng 'theshort interval of` each cycleoffthe falternati-ngcurrent source I4 when the gaseousfdischargeltube-SZis conducting, there is thus '-impressedbetween thev anode "I I andcathode "W2 yafhighdirect `4current :voltage to `cause -the production-cf high power, ultra-high frequency-oscillations which are picked up bythe loop 73 'land-transmitted throughlthe'coaxial conductor line "T51-tothe Adirective transmitting antenna II. A 3 micromicrofarad condenser IGand a ;003f1micromicrofarad 'condenser.'v'I-'ifconnectedin seriesbetween the anodelof tube t2 and ground,.arelalso charged by currentl'from source Iii through a'circut comprising ,transformer-BI]yresistorfEB-Landfinductanceielement 63. The discharge ofthe condensers.through the anode-cathode Apath-"of tube SZlthrough-thebriefxintervalfwhen the .tube is conducting .causes a .negative:starting limpulse (iaofFiglA) to'v be impresseduiconthe coaxialconductor'line' which transmits the impulse to-.the `start-Stop circuitiI6.

The startffstopcircuitl Vemploys an electric discharge 'device -40comprising twoltriodes, the onelf'havingY a` cathode 2H, a controlelectrodef'42 andan anode-:xand'fthe other'ha'ving a cathode .44, acontrol electrodeliiand an anode 45. Negativestarting; impulsesA fromthe coaxial conductor line 50 are iapplied through-a l'O`micromicrof-arad condenser CI across 0.5 megohm resistor RI whichis'connected between the lcontrol elec- `trode d2zandiground. The.catho'defdl is connected to ground. The anode43.'.is1'directly'conconnected to the controllfelectroded anode 46fisconnected to fithe control guided-2 .tthrough :a '1f-condenser {.Gzzthecapacity sof Which is 50 ;micromicrofarads when themaximumarange;to; bezmeasuredii$20,000v yarjds. The cathode 2M .-Lisifconnected Sto; ground.through 120;- 000 ohm resistor R6 shunted :by 0002microfaradlcondenserziCS, Anoderpotential .is applied to the anode 43from the positivexterminalfoi300 volti-ba'tterylSI.;through seriesresistorsRf (1,000 ohms and R`3V(0.1.-megohm), the negative :batteryterminal being grounded. Positive voltage issupplied tolthe anode-'.46Afrom source 5 Ithrough seriesf-resistorsSlRlI, R8 v(40,000 ohms) andR'I('6050004ohms) "I'heLpositiveterminal of battery 5I isfalsofc'onnected'.through series resistors RII and'fR5f(60,1000ohms) ,tto Vtheicathodefill. VA 20 micromicrofarad.'condenser`LCI I .is connected vin shunt"withivrespectzto :the'resi'stor R1. A01 microfaradf condenser ICIIJ is.connected across theiseries r'current lpath comprising resistors R6,R'I, .R8 .andthe anode-cathodefpath; from lanode I6 tocathodeAlI.

"During-'2 the quiescent-period of the lstart-stop circuit I6, the`triode M 52,--43 is 'f-ully conductingvwi'th the gridf2'held at thepotential of catho`de4I-by -resistor RI, and the anode -43 is reduced toalow yvoltage `by the passage ofY anode currentfthroughR. The grid 45'isheld at apotential which is vactually negative with respect to'cathodelili Which is-maintained at about +60 volts bythevoltage'dividerR andl. lAs triode 44,-45,"46 isthus ibiased belowcut-off the anode IIB rests at-abont -+300rvolts- The circuitremainsstably in this condition'until a starting impulse is applied.

The'negative starting impulse 'from the starting impulse generator"I5-applied to the gridv42 causes' the gridI to become negative withrespect to its cathode and thel current fiowing through theA .dischargepath-from anode 153v to cathode M is decreased. As a resulttheypotentialof anode 4-3-"andof grid 45' is--sharplyA increased to producearnegative impulseatthe anodeil due to current owing through thedischarge'path from anode 46jto cathode, this negativeimpulselbeing'impressed' upongrid'42 'by way'of condenser .C8"torreinforce the starting-impulse land -thus trigger theleadingedgeofthe start-stop wave b. Thereafterthe potential of'grid risesAexponentiallytoward its asymptote atcathode potential with'altimeconstant of approximately (RI) l(C8). The active period'of'therange unitis `determined by"thetime"required'for `the potential of grid .42 to.rise to its cut-off potential. `When the .grid 4-2 reaches its,cut-'offipotentialthe stop transient occurs,- the .triode 4 I ,dL-43becoming conducting andthe grid 45cbeing 'carried'down to itsquiescentlowpotential tonnake the triode d4, 115, 46 non-conducting Thepotentialof anode 46 thus rises'sharply until triode Linges begins todraw grid current. Thereafter'the potential at anode 46"rises.somewhat'more gradually because condenser C8 yis'pcharged exponentiallyby current passing through VR0,"R"J,"C8 'andthe grid-cathodepath'oftriode 13 I ,Midi "Asthegrid-cathode irnpedance islowgthe.recovery time constantis essentially (C8) (YR-1 +RW-Which isshort'compared tothe' time constant .(RI) (CB), so that'the circuit'may-recover itsstable lWaiting condition in a time considerablylshorter than itsl active period. *The negative "portion I 'Ik of thelstart-stop wave'b/which maybe about six times (RI (C8), for example,is'produced during'the active period While triode-III,v 42,'*43iscut'oiand the shorter positive portion I8 yof -wave i b is producedduring the quiescent period when'triodev 4 I, 42,l -43 is conducting.The shortening of the quiescent' time period is believed to be due tothe omission of the usual coupling condenser between the anode 43 andthe grid 45 so that these elements are directly conductively connected.4Condenser C9 is used to prevent cathode feedback which would decreasethe gain of the triode 44, 45, 46 during the start transient. Its valueis made small so as to hasten the return of the circuit to equilibrium.

The common terminal of the potential dividing resistors RI and R8` isconnected by way of lead 52 to the timing Wave generator 20 comprisingan oscillatory circuit in the anode current path of an electricdischarge device 53, and the timing wave c from the generator isimpressed upon a phase inverter circuit of the phase shifter 2I, whichcircuit comprises an electric discharge device 54. The phase invertercircuit is connected to a circuit comprising a variable condenser C21for shifting the phase of the wave from timing Wave generator 20. Eachof the electric discharge devices 53 and 54 comprises a cathode, acontrol grid, a screen grid, a suppressor grid, and an .Y

tube 53 through 500 ohm resistor RI2, through the antiresonant circuitcomprising inductance element LI and .005 microfarad lcondenser CI5 inparallel -and through 6,400 ohm resistor RII and .003 microfaradcondenser CI4 to the tube anode, the antiresonant circuit being tuned tocause the generation of a 65.57 kilocycle wave during the interval whentube 53 is rendered nonconducting due to the negative portion I1 of thestart-stop wave b, Fig. 1A, impressed thereon. A relatively largecapacity condenser CI5 is used in order that variations of straycapacity may not affect the frequency appreciably. The oscillatory Waveis quenched by thelow impedance of `tube 53, after the positive portionI8 of the startstop wave raises the grid of tube 53 above cut-off.Positive potential from the'300 volt source 5I is applied to the screengrid of tube 53 through a circuit comprising resistor RI2, theantiresonant circuit LI, CI5 and 20,000 ohm resistor RIS. The inductanceLI and the condenser CI 5 of the antiresonant circuit are enclosedWithin a chamber the temperature of which is maintained constant by -asuitable temperature controlling apparatus (not shown) so that thefrequency of oscillation is maintained constant. The frequency of 65.57kilocycles was chosen because the period of the wave of this frequencyis equal to the time required for aradio wave to travel 5,000 yards,that is, from a transmitting .antenna to an object 2,500 yards distantand back to a receiving antenna in proximity to the transmittingantenna. In'some cases it will be desirable to choose a timing wavehaving a different period.

The common terminal of the antiresonant circuit and the parallel circuitcomprising elements CI4 and RII is connected through .001 microfaradcondenser CI S to the control grid of the phase inverter tube 54. A 100micromicrofarad variable condenser C2 connected between the control gridof tube 54 and ground is provided to permit asmall manufacturingadjustment of frequency of the oscillatory circuit, The 16 microfaradillter condenser CIS is connected from the negative'terminal of resistorRI2 to ground.

The phase inverter circuit is used to provide an accurately balancedlow-impedance input to the 'phase shifter. It also employs cathodefeedback to present an extremely high input impedance to theantiresonantcircuit, thus minimizing damping and stray capacitance eiects. The anodecurrent path of electric discharge tube 54 may be traced from thepositive 300 volt terminal through 1,000 ohm resistor R2I, 1,000 ohmresistor R20, 6,000 ohm resistor RIS, the anode-cathode path of tube 54,ohm resistor R84, 6,000 ohm resistor HI8 `and 1,000 ohm resistorRI'I toground. RI'I and R20 are equal resistances across which the balancedoutput voltages appear. RI8 is used to increase the amount of cathodefeedback for the purpose of obtaining high input impedance andRlBbalances the resistance of RI 8 in the anode circuit. The anode currentthrough R84 produces a voltage drop which is appliedto the controlelectrode for biasing it through a filter formed by .1 megohm resistorRM shunted by a .001 microfarad condenser CIB and through .5 megohmresistor RI5. This arrangement fure ther magnies the resistancecomponent of the input circuit. Positive voltage from the 300 voltsource is supplied to the screenV grid through R2I and 0.25 megohmresistor R22. The screen grid is connected to the cathode through .006microfarad condenser C2I so that the alternating screen grid currentflows through the tube without affecting the external anode and cathodecircuits.. One terminal of resistor R22 is connected through condenserC2I to the cathode and the other terminal of R22 is connected through .5

microfarad condenser C24 to ground. With re-f spect to the alternatingtiming voltage, therefore, resistor R22 is effectively in shunt with theresistors connected in the circuit between cathode and ground. Theresistance of R22 is therefore balanced by the .25 megohm-resistor RIEconnected -between'the anode and the common terminal of resistors R20and RZI.

and C23` to a phase splitting circuit comprising twoparallel paths theone path comprising 750 micromicrofarad condenser C26, a 75 micromi`crofarad variable condenser C4 being inshunt with C26, connected inseries with 3,000 ohm resistor R21, and the other path comprising 3,000ohm resistor R26 connected in series with 750 micromicrofaradcondenser`C25, "75 micromicrofarad variable condenser C3 being in shuntwith. C25.-The plate ofcondenserCZZ, going to the phase splitting circuit, and theplate .of condenser C23 also going tothe phase'splitting circuit, areconnected through 0.1 megohm resistors R23 and R25 respectively, toground.

The phase shifting condenser C27 (see Figs. Y5 and 6) comprises an outermetallic casing 85 and metallic ring stator Sii,A four metallic statorsectors 8|, 82, 83, 84 and a dielectric rotor 8'I hav-lV ing adielectricconstant materially different from that4 of air. The rotor mayalso be made 0f metal grounded or insulated from ground, but thedielectric rotor is preferable. The dielectric rotor is mounted on ametallic shaft 29 the bearings for Whic'hlareprovided:bygthefouterocasingginthe latteriralso;providingshielding;Ther-statoranembers@ .8i .1 82 .83;78 4: and. 8:aI'e;supportedcbyginsulating membersfg91vfron11V the icasing'n Theffour.-phaseavo1tagesf-,-arefsuppliedeto .the .stator -sectors 8.4 82,.- 83;and; 84 :which:A are'fequalfzin-f area andshaperand-:arefaccuratelyiparallelfto" the-ring?` sta; ton. The casing.-85 isixconnectedfto. a metallic shield-'.90 around f a first Iamplifier. stage* of-z the pulsefgenerator .to- Awhich the-foutputfof.theiphase shifterisconnected;;the shieldbeinggrounded;

It: Will :bessen f that thel potentials impresseduponopposedstatorsectorsfoffthe phase-'shifting condenser;Nare.f180-.degrees.out .ofphaseiwhile the potentials-.atanygftwo-adjacent seetorsirare 90' de; greeszoutrof; phaseAllffour.-;potentia1sv are of equal. amplitude;`

Itithegresistance RZBorithat of-.Rl yis equalfto R and the fcapacitancev of; G2-eand fC4f'in. parallel orithatofaCeandfC-3 in paraliel is.equal to C, theneach of the:twofparallelfpatha ofthe phase splitting;lcircuitf satises =-the eequationr.

where XC'. is the .capacitive. reactance...and.f. is the. frequency, Theload impedimceZipresented by.. these.. elements.. to.. the. phaseinverter.. circuit, neglecting..anygsmallileflctf C2l.lf.is..

Under this-- conditionthe` 4loaolfimpedances'- Z1 equals for;all.'frequenciesf.-` upato; a, highv harmonic' of thertiming Wave.:whiclr-pthereforeappears undistorted: onf-stator. sectors;- 8lffi andi83. The;y phase shifted.; Wai/'esion; stator;sectors;s8.21'V and;V 84":ape proachrthein steadygstate condition: by Wayy of anrexponential-startingtransientthe= time cone stant of;- which".` is;equal..zto.-RC.:. Since which correspondstdone radianl of. the-:timingtheamplitude lbalance yof. the--voltages-.ona the four.I staten.sectors.h and-upone the similarity of therfoursections. of. the.condenser C21..

Thegringngstatorof the-phaseshifter is con.- nected byflead- 49 f tovthe Yinput of a twofstage amplierf comprisingfelectric discharge tubes9i ari-m92; andf. the output-of the amplifier isconnectedtosantimingfpulse generator circuity compulsing.,electric.:discharge-.tubes 93-eand..94; The lead 49 is connected to thecontrol grid offtube 91 Anodepotential -is suppliedto .the-.tubeiromthef 300r volt-.source 5l Ithroughl 1,0.00frohm reisistor. R37Fr and.100,000 rohm-r resistor4 R31, the cathode `of,.the ,tube 9 l-` beingconnected.. through 500 ohm :resistor- R3El to ground... Control gridbiasing. potential is. provided due to--the anode current..owingythrough R30; which bias isfsupp lied.-to.the.grid through .1megohmresistor R28 and,.2 .megohm. resistor.R29 in series- A- .01microfaradecondenser C28 .ina pathfconnecting the.A cathode oftube 3Ifto. the. commoneterminal of..resistors R28. andRZQby-passesalternating components` of the.. voltage across. R30: Screengridvoltage.issuppliedto tube 9i.. from the'300 volt. source throughresistor R3 .L andr through v.5 megohmxesistor. R32. A .01 microfarad.vcondenser C'30 connectedbetween.-thescreen grid and theathoda The anodeofy tube. 9l-..is'..con nectedltlirouglr..01-V microfarad. condenser C29.to the controlgridgof; ampliiier. tube..92.. Anode voltage .is.supplied to..tube. 92,-.from-the00.. Volt source..through resistorRS'I-and. 20,000 ohmrefsistor R36 andscreen gridlyoltage...is..vsupplied fromthe 300 volt source .throughresistor R31 and 60,000 ohmresistonR38,.thescreen .gridbeing connected through .1micromicroiaradcondenser C32 to the cathode. Resistor R35' of .lohms isconnectewbetween the' cathode of.tube 92 and'ground'to producea gridbiasinggvoltage due t'oanodercurrent owing therein, which bias issupplied to-the gridthrougn th'epl megohm resistor'R34? Condenser C3! of.1 microfaradv suppresses alternating' components ofv the voltageacrossffRi Negative feedback is provi'dedby connecting anodeof'tube'92-through .3 megohm resistor R33'1to'thecathode of tube 9|'. The use offralarge resistor for R2 StOgetherWith the negative-rfeedback makes the`input impedance of Vthe amplier. 4extremely high so that noAappreciable resistivefcomponent "of current is drawn throughther-Verysmallcapacity of the phase shifting con-denser C21;Displacement of the center-line ofxtheatiming. wave. (particularlyduring the rst few'fcycles of'each train) with? the'resultant er'-rorsrin'rangeindications'are thus avoided.v Condenser C34fof'.5-microfaradisconnected between ground and one'terminal of'resistor'R31to sup'- pressvoltage variations-lof the'300 volt source.

Thefamplieditiming yWave voltage at'the anode of-.rtuber92 'is-impressedthrough- .01 microfarad condenserC33 uponthe control gridof a centerclipper?j tube. 93;` Theicontrol igrid is-connected through-..1 megohmvresistor R39to ground and therftube cathoder is connected through 10g000ohm resistor. R40l shunted. by; .0001. lnicrofarad condenser C36torground; Anodevoltageiszsupplied-...to tube-93 from the 300 voltsourceA through 1,000 ohmresistor R45 and 20,000 ohnrresistor Rillandscreen grid voltage is supplied from the voltage divider formed byresistor AR45, .1 megohm resistor R42` and .1 megohm resistor R43; thescreenn gridl being bly-passed to the cathode through .1 microfaradcondenser C31. The tube 93..aets as. a cathode follower for the positivehalfcyclesbt the timing wave-.impressedupon '13 its grid and it is cutoff during the negative half cycles. During the Ypositive half cycle onthe grid when the grid potential rst increases and then decreases, theanode potential decreases and then increases. While the tube is cut offthe anode potential is constant. The anode of tube 93 is connectedthrough .001 microfarad condenser C35 to the grid of electric `dischargetube 94, the cathode of which is grounded. Anode voltage is supplied totube 94 through resistor R45, through 1,000 ohm resistor R41 and through5,000 ohm resistor R46. Screen grid voltage is supplied to the tubethrough resistor R45 and .1 megohm resistor R49, the screen grid beingconnected through .1 microfarad condenser C38 to ground. Condenser C65(0.1 microfarad) is connected from the negative terminal of resistor R45to ground. During the quiescent period when no wave is generated by thetiming wave generator, the control grid of tube 94 is at a slightlypositive potential, the 300 volt source connected through resistor R45and .1 megohm resistor R44 to the control grid causing a small gridcurrent to flow. During the active period when the timing wave isgenerated, the change in anode potential of tube 93 causes the gridpotential of tube 94 to be sharply increased at the beginning of onehalf cycle of the timing wave and to be sharply decreased at thebeginning of the following half cycle so that tube 94 is made conductingand non-conducting alternately. As a result, a train of square waveswith sharp corners is produced at the anode of tube 94, which isconnected to the step impulse generator 28, and at the common terminalof resistors R46 and R41, which is connected to the RC delay circuit.Differentiation of the square waves produces alternate negative andpositive sharp impulses e. Y

The RC delay circuit comprises four electric discharge tubes 95, 96, 91and 98. The squaretopped wave from the start-stop circuit is impressedupon the control grid of tube 95 through .1 microfarad condenser C39,the control grid Abeing connected to the cathode through 1 megohm gridleak resistor R5|. There is provided a current path from the 300 voltsource through 8,000 ohm resistor R50, through constant voltagedischarge device or cold cathode tube v| and through 4,000 ohm resistorR49 toV ground. The resistance of the constant voltage device changes asthe current through it varies to maintainr the voltage across the tubeconstant. A |6 microfarad condenser C40 is connected from the commonterminal of resistor R50 and cold cathode tube |00 to ground. Thecathode of tube 95 is connected through resistor R49, having .1microfarad condenser C42 connected in parallel therewith to ground, tomaintain the cathode potential at substantially 50 volts positive withrespect to ground. During the quiescent periods when the start-stop waveis positive, anode current flows through tube 95 from the 300 voltsource, through 8,000 ohm resistor R50, through 200,000 ohm rheostatR52, through the anodecathode path of tube 95 and through resistor R49to ground.

A 1,500 micromicrofarad condenser C4| connected in parallel with 150micromicrofarad condenser C43 and rheostat and R52 is thus charged to avoltage equal to the voltage drop across the rheostat which, of course,will depend upon the rheostat setting. A trimmer condenser C of 100micromicrofarads is connected in a circuitV from the anode of tube 95through .005 microfarad protetingcondenser C44 vto groundV to provide anadjustment of the time constant 'of the circuit (R52) (C4|).. Screen4grid voltage is supplied from the 300 volt source through 30,000

ohm resistor R53. The anode of Vtube is connected to the control grid ofthe cathode follower tube 96 having its cathode connected through 20,000ohm resistor R54 to ground. Anode potential is supplied to tube 96 fromthe 300 volt source through 1,000 ohm resistor R55. The cathode of tube96 is connected lto the control grid of tube 98 which, in turn, isconnected through .1 megohm resistor R58 to the mid-tap of transformerwinding 99 which supplies heating current to the cathode heater of tube96. Anode potential is supplied to tube 98 from the 300 volt sourcethrough resistor R55 and l megohm resistor R60. The common terminal ofR50 and the cold cathode tube |00, which is maintained at substantially200 volts positive with respect to ground, is connected through V35,000ohm resistor R51 and 60,000 ohm resistor R56 to the cathode lof tube 96.The resistors R56 and R51 are voltage-dividing resistors, the commonterminal of which is connected to the cathode of tube 91. The 200 voltterminal of resistor R51 is connected through .002 microfarad condenserC46 to the anode of diode tube 91, which anode is connected through1,000 ohm resistor R59 to the cathode of tube 98. The initial voltage towhich the condenser C4| is charged when tube 95 is conducting, andtherefore the initial potential at the anode of tube 95, at the grid andcathode of tube 96 and at the grid of tube 98, is determined by thesetting of rheostat R52. Assume that the initial potential at thecathode of tube 99 and at the grid of tube 98 is En volts below 200volts. When tube 95 becomes non-conducting due to the negative portionof the start-stopwave impressed upon its control grid, the condenser C4Iand its trimmers will discharge through R52 and the potential at thecathode of tube 96 and at the grid of tube 98 will rise exponentiallyfrom its initial voltage toward vthe 200 volt asymptote. When tube 99 isnot conducting, condenser C46 is charged to a voltage equal vto thepotential across resistor R51 through the anode-cathod path of tube 91,this voltage being E0=F (approx.)

below the 200 volt asymptote. Timing impulses e from the timing pulsegenerator 22 are impressed upon the cathode of tube 98 through condenserC41 of 100 micromicrofarads. Condenser C41 and 1,000 ohm resistor R59provide the necessary differentiating action. When the potential at thegrid of tube 98 has increased sufficiently with respectV to its cathodepotential due to the discharge of condenser C4|, a negative timingimpulse will lower the cathode potential of tube 98 sufciently to causethe tube to conduct and the cathode potential will then also riseexponentially due to the change in the charge on condenser C46. Thecharge on condenser C46 is changed due to current from the 3070 voltsource flowing through R55, R60, the anode-cathode path of tube 98, R59,condenser C46, R51, R56 and R54 to ground. Thus during an intervalwhichV varies with the setting of rheostat R52, the condenser C4|discharges to suchapotential that the tube 98. isfpaused tozconductfatsthe 1 instant Ithatsa-certain:negativerr impulse from'gthez: timing,4impulse generator;.isimpresseduponfits-.cathodeg A sudden; decreasefinivoltage.l is 'thereforelpro ducedV at Vthe anode tof ftubez982= The;operation of the RC del-auxcircuitv Willfzbe further.l clarified by;reference tofthe-:curvestfoi Figz, rIyvhichwill be discussed later:

The: pedestal andi" sweep-r wave generator 25compris-efelectrica-discharge 'devices 10|, |02 and |03.: The =devicez|ircomprisesftwo triodes, the onef'h'avingacatlode:| 01%,; a controlgridfi 00 and anzanode'clfandthe otherihavinga cathode |01,aicontrollgrdlilifandtananode 00. The fsharp negatiw:1 pulsevproducedafat:thefan'odeo Atube' 90 ofi' theiRC delay: 'circuitr'isimpressedithrough 100 -micronlicrofaradti condenser; C585 upon:I thecontrol?r grid? zitozfinterrupt the "flow of anode currents which i isisupplied=- trom the 300'. volt source through. 1,000 ohm: resistor R61;.1 megohmresistorRS Vto the anode- |00 the cathode': lffbeingfconnected` through '20,000 ohin re sisto R021?shunted'rby.v .lrnicrofarad'.v condenser CdSs-tbi-ground; The grid :is connected.through 5 megohmzgridlalc: resistor `R|| toA the cathode. The: anodefis-:connected through, 100 micromicrofaradfcondensertc and-50,000 ohmresistor Rrto the control grid; |08. Thus when the anodeg currentw isVinterrupted. in triodev |04; |05, Hliifa positive; impulse isimpressed', upon` the grid'rtofcause anode current to vilow from the300z-voltfzsource through; resistors yR01 "and R50 (1 1negohm)',the?anode-cathode path and R62 tofground.: The triodexllt, |08, |091mustremain conducting until-l-the'pedestal impulse and sweep Wavef--arecompleted and'therefore the resistor Riigistusediin therpatl'i" betweenthe anode |06 and-ftheigrid'.|08to;block; any-"pulses which maybe;passed throughztube- 00 andthetriodel |04; |05', |0E1by 'way'oftheplate-.togrid capacitances.l Electric:` discharge -tube |02 is; altriode having-a controlf gridg=a cathode and an anode; Discharge tubelfhasra cathode ||0andanodes-lll and ||2, formingz twor diodes; It alsohasan anode |`|3vand af. control` grid ||4"Which,awith thecommcnfcathodefl i0,- formal triode.V Anode- |00 is connected through-100xmicrcmicrofarad con'- denser C53 to the grid .of tube ,|02` andthrough 100 micromicrofaradcondenser C55 to the grid ||4 of tube |03.When triode` |01, |08, |09 is made-l to i conduct. its anode'- Voltagevdrops from plus 300 voltsfI-tota: yW-s-valuefY The grid'of tube |02 andthe grid ||4 of tube |03, which are normally slightly above cathodepotential, are thus carried negative about 150 Volts. After the gridsoftubes" |021- and |031 are thus displaced negatively; ,the'g-rid'potentials rise exponentially toward plus 300'ivoltsfdue to thecharging'of Acondensers- C 5'3fandC55through resistors R081 1 megohrn)and/2R13."A (.25 megohnr)A respectively, from'the *voltageT drop-.acrossR60:V The triode |02 fandfthe trioderportion of'tube v|03 'are thusmade' non-conducting dueto the negative impulsevfrom the RC delaycircuit and, after a short interval; theseftriodesagain becomevconducting.

Anodecurrent issuppliedto-ftube |02 lfrom=the 300.E voltsource" throughresistor R61 and`.2 megohnrv resistor R09;A the cathode beingconnested-'through 50,'000`ohm resistor R10 shunted by.0015' microfarad'condenser C52 to ground; Anode :current is applied to: the triodeoftube`|03 fomtheaSOOlvolt source through R61 -and .1 megohmi resistor;R14;4 the cathode l'lfbeing grounded. A; horizontalV sweep Wave forlthe. delction-offal-cathoderaysbeamr is zproducedi due :to

l0 when.the'start-stopwave-is positive, the lead 2| 4 is--StabIy'located-at ground `:potential asvv required forthe sweep amplier duetothe lead-2 |.4being connectedV tothe :anode Lof ,one of'the'diodes of'tube |03... Similarlyfwhen the triode portion of.y tube |03-'is`cut...oii.its.plate potentialrises momentarily toproduce:aksquareftoppedimpulse or pedestal;y g.V which is.- impressed,through. 2 megohm resistor R12,.shunted.by .001.microfarad condenserC5E.uponlead'.=2.|5 gongltothestep generator 28.' By 'connecting thelead- 2 5V to the anode rl |Loira-.diodegoiftube.. 03;- the -pealeofthepedestalH is.,` located., at., approximately ground potentiaL-.the majorpart .of the. Wave` being ,held cor-respondinglyfv negative.

The-V DedeStaLimpulse, is. supplied throughlead 2| EwandY 10,000:ohmresistor R15 ,.to, the vcontrol grid cfa electric` discharge .idevice .Y 6,;of theA -step generator 28..v The. timing impulsesirom. thetiming pulse generator 22,:are: also impressed upon the grdb tube,S-.by.fvvay of. lead- |1.` and,..20 micromicrofarad V condenser.v(l5-1.4 Inthis case, dii-erentiatione-of thefsquare AYwave from theanode of tubeBQ-is performedvby-:CE- and 7R15, resulting in-v thesharppulses ;fe-... Anode-current is'-supl plied .totubes'l 6 from 300Yv-oltsourcenl `through 13000.r ohmiresistor: R18fandga1 megohm resistor.R11 totheanodef Current,A is-also supplied from the 300 voltsource-:through-the voltagedividing resistors.- R10 .f of@ .1megohm-:fandsR165y of 15 000 ohms;- whi'ch is' Ashuntedlbyf;.01=microfarad con*- denser C58; the-.positire terminal-oflresistor. R16 being connected', tonthe i' cathode Vof tube? E I6 tomaintainaitv at a positiven-voltage:with respect to ground.-IAScreen-,gridJ voltage is supplied from the 300-voltf: source 4throughresistors: R10 and R80 (10,000 ohm's therscreen' :gridnbeing connectedthrough: condenserr4 C50 of" .0005 x microfaradto ground; The;ynegativevterminal 4o resistor-R18 is." connected through.- .1-:microfaradf` condenser C|i3ftofvgroun'd.A Theffanode'o tube |6- -isvconn'ected, throughr micromicroiarad -condenser Clfand finffshunttherewith a Acircuit comprising 2 Y megohm resistorRS l'andeOOlmicroiarad condenser -CSI In^series; tozazshortlength o'coa-xialconductor cable |goingitoiaf-Vertical deflectingplate?|221'of.the'cathode'rayxtube |25;l The other verticaldeecti-ngplate and one Iofthe horizontal d'eecting-platesv |2|faregrounded; A circuit comprising; resistorf'RB'Z'or 200'ohms in serieswith- "micromicrofarad" condenser C62 and in shunt with .said'fseriesicircuit ai .li megohmv resistorR83=is connected .between the coaxialconductcr cable ||8andfground-. Whenvthe tube l'lcpasses' anodeLAcurrent "dueto the pedestal puls'eeimpresse'dY upon Aitsacontrol grid asharp negative impulse is produced at.thei anode of tube IIS:andrimpressedmpon' the. coaxialconductorcable ||8;l condenserC02` beingcharged very:rapidl$r to aboutilOvoltsr negative With respectitto'.;groundi Cbntinued' flow offcurrent is limited' by.` means. of smallby-pass condenser C5931 in 1 the f screen:y` grid f' supply circuit andthe smallcoupling.condenser.C60: Resistor R83 providesiadischargefpathtforrthe'discharge of condenser.'CB2 to formthelexponentiallywrisingportion of the step wave i.. .Resistor .RBI andcondenser C6I in series are connected in shunt to C60 to improve thewave form of the step.

In addition to the vertical and horizontal deecting plates, the cathoderay device |25 comprises a cathode II9, anodes |20, and a phosphorescentscreen |23. At the time that the pedestal pulse g is started the sweepwave his also started and the latter is impressed `upon the horizontaldelecting plates |2| .from the output Vof the sweep amplier II5. Thestep Wave from, the step generator and the echo pulse from the output ofthe radio receiver I3 are impressed upon the Vertical deflecting platesV|22 of the cathode ray tube. The step impulse and the echo impulse arethus visually reproduced upon the screen |23 and, due to the echo pulsesbeing received and the` step or range impulses being produced insuccession at a rate within the period of persistence of vision, theecho indication is stationary upon the screen When the object from whichthe echoes are ,receivedv is stationary, and the range impulse or stepis always stationary upon the screen. By rotating the shaftsof the phaseshifter and RC delay circuit by means of a handle |26, lthe echoindication may be caused to move across the screen until the echopulseis aligned with the stepand the distance to the objectmay then bereadupon the revolution counter, or distance indicator |50, which iscalibrated in units of distance.

The circuit arrangement shown in Fig. 4 is a modication of a portion ofthe range unit which may be substituted for theportion of Fig. 3 belowthe line X-X. The circuit, arrangement is like that shown in Fig. 3 (thecorresponding parts being similarly designated) except that the portionof the circuit of Fig. 3 including tube |02 for causing a sweep wave tobegenerated is omitted, the diode anodes |II and II2 being conductivelyconnected, and that the condenser CI of 0.1 microfarad and 1,000 ohmresistor R|00 of Fig. 4 are used instead of the circuit comprisingvelements RBI, C6I, C60, R83, C62 and R82 for connecting the anode oftube I I6to the coaxial conductor cable- I I8. The modified circuit ofFig. `4 therefore functions to generate a pedestal y upon which theselected timing impulse 26 is superposed, as shown at i, Fig. 1A, andfor amplifying the selected impulse. The selected pulse orrange pulsemay be used'for some purposeA other than that of controlling thedeflection of a cathode ray beam as shown in Fig.3. For example, therange pulse from the coaxial conductor cable I I8 in Fig. 4 may be usedtogether with an echo impulse to control a means for automaticallycausing the'rotation of the shafts 29 and 34 of the variable condenserof the phase shifter 2| and of the Variable resistor of the RC delaycircuit 23 in such manner that the range pulse is maintained insynchronism with an echo impulse. With such an arrangement the range canbe read from the range indicator :|50 Without the need for manualrotation of the shafts by means *of the handle |26.

The operation of the system may be better understood from a.consideration of the curves of Fig. .7 which show the relationshipbetween voltage and time at several parts of the RC delay circuit 23, inconjunction with the diagram of Fig. 1A. Curve |29 shows the potentialat the cathodes of tubes |00 and 95. Curve |30 shows the potential atthe cathode of tube 96 and at the grid of tube 98. Curve I3| shows thepotencircuit I6 vto start the timing wave c produced by the timing wavegenerator 20. The timing Wave -in turn causes the generation of thetimingimpulses e by the timing pulse generator 22. The cathode of tubeis maintained at a constant potential of 50 vvolts positive with respectto ground and the anode of tube |00 is maintained at a constantpotential of 200 volts as indicated by curves |29 and |33, respectively.The initial voltage drop En across rheostat R52, and therefore thevoltage across the capacity in shunt with R52, varies with the rheostatsetting. The current through R52 Vis the anode current of tube 95 whichis limited to a safe operating value by the screen grid Voltage. Theinitial potential at the anode of tube 95, the grid of tube 96, thecathode of tube 96 and at thergrid of tube 98 is therefore at some valueu greater than 50 volts andless than 200 volts depending upon therheostat setting. When tube 95 is cut oi and the condenser C4|discharges, the potential rises from the value u toward the 200 voltasymptote as indicated by curve |30. With En variable the cathodepotential of tube 98 must be made a function of the range setting. Asindicated by curve I3I, this potential has an initial value below -200volts and is obtained by means ofthe voltage divider R56, R51, condenserC46 and diode 91, E being equal to 2.718 which is approximately equal tothe ratio of 35,000 ohms to 95,000 ohms, that is,

R57 -I- R56 tive impulse 33 will cause the tube 98 to become conductingwith theresult that the potential at the anode of tube 98 decreasessharply as indicated by curve I 34.

The cathode potential of tube 91 also rises exponentially as indicatedby the curve |32. When tube 98 becomes conducting, anode current fromthe 300 volt source flowing through tube 98 and resistor R59 chargescondenser C46 to cause the cathode potential of tube 98 to rise as shownby the portion of curve I3I Whichis substantially parallel to the curve|30. At the time tmax the -grid potential of tube98 is decreased, due tothe positive portion of the start-stop wave a being impressed upon thetube 95 and the ow of space current through tube 98 ceases. Shortlythereafter the potential of the cathode of diode 91 is reduced below thepotential of its'anode and the diode' passes space. cur-renti' until the'anode andi cathode of the diode lll are at the same potential. Thecathode of tube 98 is thus returned to its initial potentials o and theycircuit i's ready to bestarted by a succeeding start-stop wave` b at thetime to.

The initial decrease in anode potential of tube 98 asi indicated bycurvel |34 cuts on the triode |04, |05, |06 of the' pedestal and sweepVwave generator so that the pedestal wave g andv the sweep wave h areinitiated at the instant that the negative` timing pulse 33 occurs sothat the following positive timing p'ulse 2B will be superpose'd uponthe pedestal for producing a range mark as indicated at. i, Figi 1A.Each complete revolution of the shaft 29 in one direction or the" othershifts the phase of the timing wave in a corresponding direction throughone cycle and each` of the timing pulses is therefore shifted by anamount equal to the period of the timing wave.- Revolving the shaft 29also varies the setting of rheostat R52 to change the time constant ofthe condenser discharge circuit at suchv a rate that the intervalbetween an impulse 33 of each series of impulses which causes the tube98 to become conducting and the preceding starting impulse may be variedcontinuously in either direction over a range extend-ing from a valuenear zero to a maximum value. It is' thus seen that the impulse 26 whichfollows the pulse 33 Will be selected to produce a range mark at alltimes and that the time of occurrence of this range mark may be variedby the rotation of shaft 29, each revolution causing the mark to beproduced earlier or later by an interval equal to the period of thetiming pulse. Since the distance to the object, represented by theperiod of a single cycle of the timing wave, is the velocity ofpropagationl of the radiated impulse divided by twice the frequency ofthe timing wave, it is seen that the indicator |50 may be calibrated inunits of dis= tance so that the range to the object may be read when therange impulse 26 occurs; in. synchronism with an echo pulse receivedfrom the object.

This application is a division of my application Serial No. 491,791,filed June 22, 1943, now Patent No. 2,422,204.

What is claimed is: K

1. In combination; means for producing an initial electrical impulse,means for producing an impulse which is delayed with respect to saidinitial impulse, and` means for indicating the delay interval separatingsaid impulses comprising means for producing in response to said initialimpulse an alternating voltage having a predetermined constantfrequency, means for producing under control of said alternating voltageat equally spaced time intervals a series of alternately positive andnegative voltage impulsesin synchronism with the successive positive andnegative half cycles of said alternating voltage, a circuit comprisingresistance and reactance, means for supplying current to said circuit,means for changing the supply of current to said circuit to cause tobeset up across a portion at least of said circuit an exponentiallyvchanging voltage Wave the rate of change of which is determined by thetime constant of said circuit, means for changing the ratio of saidresistance to said re- 20 actance to vary the time constant of saidcir-` cuit, means for producing; an indication corresponding to saidtime constant, means under joint control of said exponentially changingwave and one of saidV series. of impulses having a. cer-V tain polarityfor producing a pedestal voltage upon which the succeeding impulse ofopposite polarity of said series is superposed, means for producing acathode ray beam,V means for defleeting said catho-de. ray beam alongtwo coordinates, means responsive to saidY one impulse for controllingsaid denecting means to cause said cathode ray beam to be deflectedalong one of saidcoordinates and means responsive to said succeedingimpulse superposed upon said pedestal and to said delayed impulse forcontrolling said deiiecting means to cause said cathode. ray beam to bedeflected along the other of said coordinates.-

2. In a system having means for producing an initial electrical impulseandk means for produc-` ing a delayed impulse which is delayed by adelay interval which may vary with respect to said initial impulse,means for producing an indication of said delay interval which comprisesmeans for producing during a certain period starting' substantiallysimultaneously with said initial impulse an alternating" voltage havinga predeterminedl constant frequency, means for producingalternaterpositive and negative voltage impulses in xed time relationwith` respect to the positive or negative peaks of said alternatingvoltage, means for producing anex'ponentially changing voltagecomprising a circuit the time constant of whichv may be varied, meansfor producing an indi'catiori` corresponding tochanges of saidtimeconstant,A means responsive jointly to saidexponentially changingvoltage andv to one of 'said negative impulses' lags said initialimpulse by a period substantially equal te the time constant of saidtime constant circuit for producing a pedestal voltage upon which thesucceeding positive impulse is superposed, a cathode ray device havinghorizontal and vertical deflecting means for deflecting a cathode raybeam, mea-'ns' under control of said negative impulse for producingl awave for causing the cathode ray' beam to be deflected horiaontallystarting at the time ofV said negative impulse, and means responsive tosaid positivev impulse superposed on saidpedestal and to said delayed!impulse for causing vertical deflection of said cathode ray'bea'm.

3. Apparatus in accordancer with claim 1 in which is provided means forcontinuously shifting the phase of saidalternating voltagel by an amountdetermined by' the change of the' time constant of said' cli-"ouinv 4.Apparatus` in accordance with claim 2 in which is provided. means forsimultaneously changing by corresponding amounts, the time constant ofsaid circuit of the phase of saidal* ternating voltage; A

LARNED A. MEACHAM.

EFRS CITED llie following references are of record in the nle of thispatent:

UNITED STATES PATENTS

